Dual purpose dimple for HVAC circular ductwork

ABSTRACT

HVAC ductwork is sealed along its joints in order to reduce air leakage. The ductwork can be sealed by the combination of a gasket and mechanical locking mechanism. Transverse mechanical locking joints are provided.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation-in-part application of Nonprovisional applicationSer. No. 12/133,482, filed Jun. 5, 2008, which issued as U.S. Pat. No.7,992,904 on Aug. 9, 2011, which claims the benefit of ProvisionalApplication Ser. No. 60/942,412, filed Jun. 6, 2007. This applicationincorporates by reference Nonprovisional application Ser. No.12/133,482, filed Jun. 5, 2008, which issued as U.S. Pat. No. 7,992,904on Aug. 9, 2011, and Provisional Application Ser. No. 60/492,412, filedJun. 6, 2007.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to a connection for HVAC ductwork. Thisinvention specifically relates to a sealing mechanism for HVAC ductworkthat reduces air leakage in joints.

2. Description of the Related Art

Traditional ductwork has air leakage at the joints. There has been aneed to add a gasket material to the joints so that when the ductwork isconnected little leakage occurs. However to be able to add a gasketingmaterial during the manufacturing process the gasketing material wouldhave to have the following properties:

1) Good adhesion to sheet metal;

2) Minimal surface tack; and

3) Short curing time.

There are numerous materials that have two out of the three qualitieslisted above but it is very difficult to find one having all three.Therefore, adding a gasketing material to the manufacturing process hasbeen impractical. Typically in ductwork manufacturing it would takethree seconds to form the longitudinal seam and then roll the sheetmetal duct for shipping. As an example of how traditional gasketingmaterials would make the manufacturing process difficult one could lookat adding a sealant that does not set up quickly. The sealant would havegood adhesion to galvanized steel and little surface tack but does notset up quickly. It could take two to three hours or two to three daysfor the gasketing material to set up or cure. This length of time is notpractical as either one would have to wait for each individual sheet tocure or you would have to have some type of stacking systems where thesheets are not touching each other. This would make volume manufacturingin a timely fashion impossible. Additionally, if the material sets upquickly but has too much surface tack it will cause problems in theshipping when the ducts are nested together.

U.S. Pat. No. 6,325,389 entitled “Self Sealing Fluid Duct/FittingConnector” describes the problems in the prior art with ConventionalHVAC systems. It describes the air leakage at the joints withtraditional ductwork. The solution in 6,325,389 is a special connectorfor the ductwork with a sealant.

There is a need for sealing the connections between ductwork withouthaving a special fitting that is incorporated in the connectionsmanufactured into the ductwork.

SUMMARY OF THE INVENTION

This invention provides for a method of connecting two pieces of HVACcircular ductwork during installation of the HVAC ductwork includingproviding a plurality of circular ductwork. The circular ductwork canhave a female end; a male end for connecting with a corresponding femaleend on another piece of circular ductwork so that two pieces of ductworkcan be connected; a push-lock female transverse positioning lock on thefemale end; and a push-lock male transverse positioning lock on the maleend capable of engaging with a corresponding female transversepositioning lock on another piece of circular ductwork. The method caninclude inserting the male end on a first piece of the provided circularductwork into a corresponding female end on a second piece of theprovided ductwork. The method can also include engaging the push-lockmale transverse lock on the male end of the first piece of providedcircular ductwork with the corresponding push-lock female transversepositioning lock on the female end of the second piece of providedcircular ductwork thereby connecting two pieces of circular ductwork sothat the two pieces of circular ductwork do not slide apart and becomedisconnected without disengagement of the push-lock male transversepositioning lock on the male end of the first piece of provided circularductwork from the push-lock female transverse positioning lock on thefemale end of the second piece of provided circular ductwork.

The push-lock female transverse positioning lock can include a fastenerstarter that serves as a guide for a fastener. The push-lock femaletransverse positioning lock can be a dimple that acts as both the femalepush-lock mechanism and the guide and can include multiple dimples thatcan be spaced less than eight inches apart around the female end. Afastener can be inserted into a dimple. The push-lock male transversepositioning lock can be a bead created that corresponds to the dimple.

The male end can have a stop bead that prevents the male end fromtelescoping within the corresponding female end of another piece ofcircular ductwork when the two pieces of circular are connected.

This invention also provides for a method for manufacturing HVACcircular ductwork including providing a coil of sheet metal having afemale side that will be formed into a female end of the ductwork and amale side that will be formed into a male end; forming a push-lockfemale transverse positioning lock on the female side of the sheetmetal; forming a longitudinal locking mechanism; cutting the sheet metalto proper length for ductwork; forming a female end; forming a male end;forming a push-lock male transverse positioning lock on the female sideof the sheet metal and forming the sheet metal into a circular ductform. The push-lock female transverse positioning lock can be a dimple.The dimple is formed on sheet metal after it comes off the roll butprior to the sheet metal being cut.

This invention also provides for a circular sheet metal duct havingsheet metal formed into the shape of the duct having a female end, amale end, and a longitudinal snap locking mechanism; locks formed intothe longitudinal snap locking mechanism, the locks having a frequency ofgreater than two inches; and a notch in the longitudinal snap lockingmechanism on the female end. The HVAC circular sheet metal duct caninclude a push-lock female transverse positioning lock; a push-lock maletransverse positioning lock; and a gasket on the female end that sealsthe connections of the duct. The push-lock female transverse positioninglock can be a dimple.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a single section of round ductworkshowing a male end of a section of round ductwork.

FIG. 2 is a section view of a male end of the ductwork along sectionII-II.

FIG. 3 is an isometric view of a single section of round ductworkshowing a female end of a section of round ductwork.

FIG. 4 is a section view of a female end of the ductwork along sectionIV-IV.

FIG. 5 is an isometric view of a single section of round ductworkshowing a female end of the ductwork having a bead.

FIG. 6 is a section view of a female end of the ductwork having a beadalong section VI-VI.

FIG. 7 is an isometric view of a single section of a ductwork having aflared female end.

FIG. 8 is a section view of a female end of the ductwork having a flaredfemale end along section VIII-VIII.

FIG. 9 is a block diagram of the method for forming ductwork.

FIG. 10 shows a first embodiment of a female transverse positioning lockand a male transverse positioning lock.

FIG. 11 shows a second embodiment of a female transverse positioninglock and a male transverse positioning lock.

FIG. 11A is a section view of a longitudinal snap locking mechanism.

FIG. 12 shows a third embodiment of a push-lock female transversepositioning lock.

FIG. 13 is a third embodiment of a push-lock female transversepositioning lock and a push-lock male transverse positioning lock.

FIG. 14 is a section view of a longitudinal snap locking mechanismhaving locks.

FIG. 15 is a block diagram of the method of manufacturing the circularductwork.

FIG. 16 is a block diagram of the method of installing the circularductwork.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Definitions

“round metal heating ventilation and air conditioning duct forresidential or commercial use”—a cylindrical tube used to transportair—this includes spiral, round and oval ducts.

“forming a male crimped end and a female”—creating two ends used toconnect ductwork together in the sheet metal.

“forming a longitudinal latching system on the sheet metalduct”—creating a mechanism in the sheet metal to connect ends of theduct so that it creates a round metal duct.

“gasket”—any type of sealing material that reduces air leakage betweenthe joints formed in the ductwork. This would include a preformedproduct that has a tape on it and can be applied to the duct. Loctitenuva sil 5039 is an example of cured gasket material.

“cured”—process by which gasket hardens or toughens or turns into agasket. Can be cross linking of polymer chains.

“first state”—any pre-cured state. Could be a liquid or other state ofpolymer or other material prior to reaching its final hardened or curedstate as a gasket.

“adheres to the sheet metal”—attaching to the sheet metal.

“minimal surface tack”—when ducts are shipped they are nested againstother ducts. The surface tack would be such that the ducts would notstick together and/or would not damage the gasket. This could beaccomplished by putting a tape material on one side of the gasket. Agasket with a tape would be a gasket with minimal surface tack. Also anuncovered gasket that does not stick to other ducts would be a gasketwith minimal surface tack.

“Ultraviolet”—(UV) light is electromagnetic radiation with a wavelengthshorter than that of visible light, but longer than soft X-rays. It isso named because the spectrum consists of electromagnetic waves withfrequencies higher than those that humans identify as the color violet.

“foamed”—injecting some gas or blowing agent causing the gasket to growcreating bubbles in gasket causing the gasket to be more compressible. Agasketing material that has gas bubbles. A Nordson foam mixer could beused to foam the gasketing material. It is desirable to foam the gasketbecause less gasket material can be used. If it is foamed at 50% then50% less gasket material is used.

“sealed joint”—a ductwork joint that has less leakage than a ductworkjoint without a gasket.

“ductwork”—includes other straight pieces of duct and all types offittings.

“round metal duct”—a cylindrical tube used to transport air.

“male end”—designed with a projecting part for fitting into acorresponding female part.

“female end”—designed to be hollow or have a groove into which acorresponding male part fits.

“a bead”—an impression formed into sheet metal.

“a longitudinal snap locking mechanism”—something that allows two endsof duct to be joined together without a separate fastener. Examples ofthis are a button lock and a reeves lock.

“sheet metal duct”—any type of duct work.

“applying an agent”—using an agent as to aid in the curing. It could beultraviolet light, radiation, moisture, catalyst or light or anything tohelp in the curing.

“a female transverse positioning lock”—portion of transverse positioninglock on the female end.

“a male transverse positioning lock”—portion of a transverse positioninglock on the male end.

“transverse positioning lock”—any type of mechanical structure thatallows two pieces of ductwork to be rigidly joined together or lockedtogether.

“push-lock”—an integral mechanical coupling on the ends of ductwork thatallows the ducts to be pushed together by force and locking the ductstogether.

“lock”—a button lock or a reeves lock.

-   2—circular duct-   4—crimped end or male end-   6—male bead-   8—female end-   10—gasket-   12—leading edge-   14—female bead-   16—inside of female bead-   18—flared portion-   20—lock-   22—second bead or push-lock male transverse positioning lock-   24—cut out or notch-   26—push-lock female transverse positioning lock-   28—dimples-   30—fastener or a screw

DESCRIPTION

FIG. 1 shows a circular duct 2. Male crimped end 4 has a male bead 6.The male crimped end 4 is designed to be inserted into female end 8 ofanother duct.

FIG. 2 shows section II-II of FIG. 1. Fast curing gasket 10 is on aleading edge 12 of the male bead 6. The fast curing gasket 10 isproximate to the male end 4.

FIG. 3 shows a second embodiment of a circular duct 2. The fast curinggasket 10 is proximate to the female end 8.

FIG. 3 shows section Iv-Iv of FIG. 3. Fast curing gasket 10 is proximateto female end 8.

FIG. 5 shows a third embodiment of a circular duct 2. The female end 8has a female bead 14.

FIG. 6 shows section VI-VI of FIG. 5. Fast curing gasket 10 is locatedon an inside of the female bead 16.

FIG. 7 shows a fourth embodiment of a circular duct 2. Female end 8 hasa flared portion 18.

FIG. 8 is a cross section along VIII-VIII of FIG. 7. Fast curing gasket10 is located in the flair portion 18. When a male crimped end 4 isinserted into the female end 8, the male crimped end 4 is able to enterwithout touching the gasket 10 and the gasket 10 seals on a non crimpedpart of the crimped male end 4.

FIG. 9 is a block diagram of the method of making the circular duct.Sheet metal is cut off of a master coil and travels down a conveyor. Thesheet travels into a machine where it may or may not get clipped. Theoptional female bead can be put in the female portion or the flaredportion could be created. Optionally at the same time the gasket may beput onto the sheet at that time. Paper or some sort of covering agentmight be placed onto the gasket so that it doesn't stick to adjacentpieces of ducts during shipping thereby making it have little surfacetack. By doing it this way it gives the fast curing gasket time to cureand if release paper is used it is a nice flat non stick surface at thispoint. The gasket may travel under ultraviolet lights to cure.Additionally other agents may be used to increase curing time or aid incuring of the gasket.

The sheet will then travel down the conveyor to the roll formingmachines where the longitudinal snap locking mechanism is formed andoptionally sealant is applied. This can be seen in application Ser. No.11/739,238 which is hereby incorporated by reference in its entirety.

After the longitudinal snap locking mechanism is formed the male portionis formed by crimping an end of the sheet metal. At this same time themale bead is put on.

At this time applicants believe that the preferred embodiment would addthe gasket after the longitudinal snap locking mechanism but prior tothe male portion being formed. The gasket material is Q′ so Q63-40 andpreferably is foamed when used in this application. It is foamed by aNordson Foam Melt 200. The foaming helps with the compressibility of thegasket. The compressibility could be determined in a manner of hardness.The hardness could be measured by a durometer and have a hardness lessthan Shore A 75. Preferably it would have hardness of Shore OO in therange of 30-50.

A section on the end of the sheet metal may be notched out so that thelongitudinal snap locking mechanism stops short of the bead so that itis not crushed when the longitudinal snap locking mechanism is formed.The notched out part helps to form a better seal because the maleportion can fit better into the female portion.

The male and female sections can be put together and a sealed connectionis created without having to take any further steps. When discussing asealed connection it is meant to refer where minimal air leakage ispresent or less leakage than when there is no sealant in the connection.

FIG. 10 shows a first embodiment of a transverse positioning lock. Onthe female end 8 of a duct there can be a lock 20 which in thisembodiment is the female transverse positioning lock. The gasket 10 ison an inside of the female end 8 of the duct. The crimped male end 4 hasa second bead 22 which in this embodiment is the male transversepositioning lock. The crimped male end 4 fits into the female end sothat the second bead 22 slides over the lock 20 and locks the pipestogether and ensures that the gasket lines up correctly.

FIG. 11 shows a second embodiment of a transverse positioning lock. Thefemale end 8 of the duct has a female bead 14. The female end 8 has acut out 24 or notch (either term can be used hereinafter) on thelongitudinal seam. The combination of the female bead 14 and the cut out24 in this embodiment is the female transverse positioning lock. Thelongitudinal snap locking mechanism can be seen in FIG. 11A. A femalepart 26 of the longitudinal snap locking mechanism is removed up untilthe female bead 14 to create the cut out 24. The crimped male end 4 hasa second bead 22 which in this embodiment is the male transversepositioning lock. The crimped male end 4 fits into the female end 8 sothat the second bead 22 slides into the female bead 14 and locks thepipes together and ensures that the gasket lines up correctly andcreates a proper seal. The cut out 24 allows the female end of the pipeto more closely match the male end of the pipe and allows for a tighterfit. The cut out 24 makes the I.D. of the female end of the pipe moreround. The cut out 24 improves the gap between the male and female endswhether or not sealant is used on the ends. If the cut out 24 was notthere, the longitudinal snap locking mechanism by sticking out wouldcreate a gap between the male and female ends. If sealant is used withthe cut out 24, less gasket material is required because the gap betweenthe male and female ends is thinner with the cut out 24. FIG. 14 is asectional view of a longitudinal snap locking mechanism having locks 20.The preferred embodiment has a lock frequency of every 0.95 inches on a5 foot pipe, which would equal approximately 60 locks.

FIG. 12 shows a third embodiment of a push-lock female transversepositioning lock. FIG. 13 is a third embodiment of a push-lock femaletransverse positioning lock and a push-lock male transverse positioninglock. Dimples 28 show a push-lock female transverse positioning lock onthe female end of the HVAC circular ductwork 2. The dimples 28 engagewith a second bead 22 which is a push-lock male transverse positioninglock on the male end of the HVAC circular ductwork 2 in this embodiment.The second bead 22 could be concave or convex with respect to the outersurface of the circular ductwork 2. The combination of the dimples 28and the second bead 22 create the push-lock transverse positioning lock.This embodiment provides a balance of installation force with thelocking force. Typical installations can involve working three storiesup on a ladder or boom. This makes handling pieces of ductworkdifficult. The installer has to be careful and has great concern so thatthey do not fall off of the ladder or boom and additionally does notwant to push or pull the other ductwork that is already connected apart.The dimples could be compared with a leaf spring or series of leafsprings or the button locks which required more installation orinsertion force. Additionally with the leaf spring scenario, if thecrimped end 4 was not perfect it could cause the leaf spring to deformupon insertion and thereby not create good locking force. The dimples 28do not give and therefore are forced over the second bead 22 and thencan maintain a good juncture even if the crimped end 4 is not perfect.The dimples 28 give the right balance of retention force combined withinsertion force. The level of insertion force with the dimples 28 wouldbe acceptable to installers.

The process of creating the preferred embodiment starts with a coil ofsheet steel. The coil is either 5 or 2 feet wide. As the metal isdispensed off the coil, the first step is to add the bead for thesealant and the dimple. Those two features are added as the metal ispulled between two sets of rolls. The sealant bead is created as themetal is pulled between two rolls. One roll has a rib around thecircumference and the other roll has a corresponding female depressionaround its circumference. As the metal is pulled between those rolls,the male rib and the female depression form the bead. Next to the rollsthat create that sealant bead, there is a similar set of rolls thatcreates the dimple. In this case, the rolls are inverted so that thedimple will pop out in the opposite direction of the sealant bead.Instead of the roll having a continuous rib around the circumference,there are periodic bumps or projections. On the female roll there isstill a continuous depression around its circumference, which is how thedimple is created.

The dimples 28 are spaced with a frequency of less than 8 inches. Thepreferred embodiment has the dimple frequency 2-4 inches. The currentbest known frequency is 4 inches. The frequency could be less than 8inches, less than 4 inches, or 2-4 inches. A fastener or screw 30 canthen be inserted into the dimple.

Circular ductwork installation guidelines provided by Sheet Metal andAir Conditioning Contractors' National Association (“SMACNA”) and otherguidelines require the use of a screw 30 at the joint of two pieces ofductwork. Again it is often difficult for installers while working inelevation to start a screw into the sheet metal. The dimples 28 serve adual purpose of not only the female transverse positioning lock but alsoas guide for a screw 30. This is a big help to installers.

The transverse positioning lock can also help installers when they areputting up ductwork as it can enable them to measure and or install theductwork without drooping or sagging of the pieces without using ascrew. The installer can put up the ductwork system and measure and cutpieces without having to fasten all the pieces together with a screw.This gives great flexibility and ease in the installation process. Thetransverse positioning lock is part of the ductwork and integrallyformed into the sheet metal of the HVAC circular ductwork 2. It is not aseparate connector. Additionally, the push-luck is not a threaded screwconnection.

FIG. 15 is a block diagram of the method of manufacturing the ductwork.Sheet metal comes off of the roller from a coil of sheet metal. A femaletransverse positioning lock is formed on the female end of the sheetmetal. A dimple can be formed by a roller on a Slear machine (such asone produced by Iowa Precision Industries, Inc. under the registeredtrademark SLEAR), which is a combination of a “slitter” and a “shear,”after it comes off of the roller but prior to being cut. The metal isthen cut into proper length strips. The metal goes through a roll formerthat puts the longitudinal seam on it. The end seam gasket is applied. Amale transverse positioning lock is formed, the crimp is applied, andthe sheet metal is formed into circular ductwork given a curvature onthe pipe roller.

FIG. 16 is a block diagram of the method of installing the ductwork. Theductwork is shipped in bundles of approximately ten pieces. To installthe ductwork, the installer will take off a first piece of ductwork,then the installer will take off a second piece. The installer willengage the longitudinal snap locking mechanism to create circular ducts.The installer will then push the two pieces of ductwork together, makingsure that the second piece slides over the dimple on the first piece andit locks in. The installer will then put the ductwork up. The next stepis putting a fastener in the ductwork.

Various changes could be made in the above construction and methodwithout departing from the scope of the invention as defined in theclaims below. It is intended that all matter contained in the paragraphsabove, as shown in the accompanying drawings, shall be interpreted asillustrative and not as a limitation.

We claim:
 1. A method of connecting two pieces of HVAC circular ductworkduring installation of the HVAC ductwork comprising: (a) providing aplurality of circular ductwork, the circular ductwork having: (i) afemale end; (ii) a male end for connecting with a corresponding femaleend on another piece of circular ductwork so that two pieces of ductworkcan be connected; (iii) a push-lock female transverse positioning lockon the female end including multiple dimples spaced less than eightinches apart around the female end that can serve as fastener startersor as a guide for a fastener; and (iv) a push-lock male transversepositioning lock on the male end capable of engaging with correspondingfemale transverse positioning lock on another piece of circularductwork; (b) inserting the male end on a first piece of the providedcircular ductwork into a corresponding female end on a second piece ofthe provided ductwork; (c) engaging the push-lock male transverse lockon the male end of the first piece of provided circular ductwork withthe corresponding push-lock female transverse positioning lock on thefemale end of the second piece of provided circular ductwork therebyconnecting two pieces of circular ductwork so that the two pieces ofcircular ductwork do not slide apart and become disconnected withoutdisengagement of the push-lock male transverse positioning lock on themale end of the first piece of provided circular ductwork from thepush-lock female transverse positioning lock on the female end of thesecond piece of provided circular ductwork; and (d) inserting a fastenerthrough at least one dimple and into the male end.
 2. A method asrecited in claim 1 wherein the male end has a stop bead that preventsthe male end from telescoping within the corresponding female end ofanother piece of circular ductwork when the two pieces of circularductwork are connected.
 3. A method as recited in claim 1 wherein thepush-lock male transverse positioning lock is a bead created thatcorresponds to the dimple.
 4. A method for manufacturing HVAC circularductwork comprising: (a) providing a coil of sheet metal having a femaleside that will be formed into a female end of the ductwork and a maleside that will be formed into a male end; (b) forming a push-lock femaletransverse positioning lock dimple on the female side of the sheet metalwherein the dimple is formed after the coil of sheet metal comes off therole but before the sheet metal is cut; (c) forming a longitudinallocking mechanism; (d) cutting the sheet metal to proper length forductwork; (e) forming a female end; (f) forming a male end; (g) forminga push-lock male transverse positioning lock on the male side of thesheet metal; and (h) forming the sheet metal into a circular duct form.5. A method of connecting two pieces of HVAC circular ductwork duringinstallation of the HVAC ductwork comprising: (a) providing a pluralityof circular ductwork, the circular ductwork having: (i) a female end;(ii) a male end for connecting with a corresponding female end onanother piece of circular ductwork so that two pieces of ductwork can beconnected; (iii) a push-lock female transverse positioning lock on thefemale end; and (iv) a push-lock male transverse positioning lock on themale end capable of engaging with a corresponding female transversepositioning lock on another piece of circular ductwork; (b) axiallyinserting the male end on a first piece of the provided circularductwork into a corresponding female end on a second piece of theprovided ductwork; (c) engaging the push-lock male transverse lock onthe male end of the first piece of provided circular ductwork with thecorresponding push-lock female transverse positioning lock on the femaleend of the second piece of provided circular ductwork thereby connectingtwo pieces of circular ductwork without rotation of the two piecesrelative to each other so that the two pieces of circular ductwork donot slide apart and become disconnected without disengagement of thepush-lock male transverse positioning lock on the male end of the firstpiece of provided circular ductwork from the push-lock female transversepositioning lock on the female end of the second piece of providedcircular ductwork; (d) the push-lock female transverse positioning lockincludes a fastener starter that serves as a guide for a fastener; (e)the push-lock female transverse positioning lock comprises a dimple thatacts as both the female push-lock mechanism and the guide; and (f)including inserting a fastener into the dimple.